Broadside antenna array



July 24, 19:28.

BROADSIDE ANTENNA ARRAY Filed June 5, 1926 3 Sheets-Sheet 1 SingleWwentama,

uonwamfated VMM/remate@ Iii/ale Kronau-:lie in tema,

mu/aw a 1,90' mmmumr/maana A HUH/v5 y 1,677,956 s. w. DEAN July 24,1928. 1,677,956

S. W. DEAN lS. Weaw 5C ATTORNEY July 24, 1928.

, 1,677,956 s. W. DEAN BRoADsIDE ANTENNA ARRAY Filed June 5, 1926 5Sheets-Sheet 3 Mgr,

NI/ENTOI? /1 TTOANEY Patented July 34, i923.

UNHTED STTES ,Y senese sintesi?` Vssi-es.

SAMUEL, lW- DEAN. QF HOULTUN, MAINE, ASSIGNQR, e0 Memisa-N "DELEN-IonaAND TELEGBAPH COMPANY;

n connaissaient or new Yoan.

BROADSIDE ANTENNA ARRAY.

Application filed June 3,

This invention relates to radio transmission systems, and moreparticularly to arrangements for connecting a plurality of antennae inarray formation. i

lVhen using a wave antenna it has been customary to make use ot a smalltraction of the interference or noise voltages develcned in the surgeresistance of the antenna to balance out undesired interference or noisereceived from a direction approximately opposite to that ot the desiredsignal. lbuch a procedure is termed compensation7 and lserves in effectto deiorm the normally directive curve of the antenna in such manner asto produce zero reception atany desired angle iloehindy the antenna,that is, at any angle greater than 90 degrees measured from thedirection of the desired signal which is in linewith the antenna. Inparticular', compensation is often used to produce Zero reception at anangle of' 180 degrees, or directly opposite to the direction oi' thedesired antenna. it is also known that the directivity may be increasedVby the use of a system of parallel wave antenn spaced apart a certaintraction of a Wave length in a direct-ion at right angles to that of thedesired signal, cach Wave antenna, however, extending in the directionof the desired sig-nal. Such an arrangen'icnt is commonly called abroadside wave antenna system. The eiect ot the broadsidevarrangement ingeneral is to decrease the Width of the directive curve as measured in adirection at right angles to the axis of transmission. In such a systemcompensa-tion of the individual antennae is capabler ot reducing to aconsiderable extent the size of the so-called back-end area ot thedirective diagram. In other words,` the cception `oit 'interference andnoise over the entire semi-circle to the rear ot the antenna system isreduced with a corresponding` iml'irm'ement ot the signal-noise orsignal-interference ratio.

in the past this compensation has been accianplishe-d by separateadjustments for cachantenna of the liroadside system, that is, each`antenna has been compensated by itselt as it it vWere to he used aloneand the outputs oi the antennae have been subsequently combined in asuitable manner. in accordance with the present invention it is proposedto bring to a central point voltages derived from the surge resistancesof 1926. Serial N0. 113,505.

the several antennae of the broadside system and combine them in thesame manner as the desired signal (derived from the so-called 4"irontendy oi' the antennae). Having thus combined these interference andnoise voltages from the several antennae it is proposed to` utilize, aportion of the resultantvoltage to balance out noise and interferencevoltages coexistent with the desired signal in the circuit derived:liromthe lfront end77 of the antennae. In doing this the same generalresult is obtained as in the case of the individual compensatingVmethods previously used, but the result is obtained in a simplermanner. llurthermore,` the proposed compensation has the advantage thatit permits ot a very much more accurate adjustment ot the balance thanIhas ever been possible Where it was attempted to balance' each antennaseparately.

Another feature oit the present invention relates to the details oif thecircuits tor .conihining the outputs oi' several antennae connected inparallel. it, for example, lines from a plurality ot Wave antennae areconnected to the pri-maries oi similar transformers Whose secondariesare connected in paralleltol a common receiver, or if the line-s areconnected to the primaries ot a multiple.

winding transformer `Whose secondary is connected to. the receiver, thelines will not be terminated in their characteristic impedances. Forexample, Where we have three antennae each line 1would be terminated inthe impedances of the other two lines together Withthe input impedanceof the receiving apparatus-Pall in parallel. This would obviously heconsiderably less than the characteristic impedance ot' the line. Inaccordance with the present invention it is therefore proposed tocorrect this dii'iiculty by building out7 'he ytranstormers withimpedance networks in such a manner as to terminate all ot the lines intheir characteristic impedances.

rihe method of compensation and impedance correction ot the presentinvention are equally Vapplicable to other types oi: directive antennasystems when arranged in thread-mild?, as ivill be described later.

rEhe invention may new be more fully understood trom the followingdetailed description when read in connection with the accompanyingdrawing in which Figure l shows `they invention as applied to a systemlill) llU of wave antennae connected in broadside; Figs. 2, 3, l and 5are curves or directional diagrams illustrating the directivecharacteristics of wave antenna systems; Figs. 6, 7 and 8 are diagramsshowing alternative methods of combining the outputs of a number ofseparate antenna systems; and Figs. 9 and 10 shoiv the invention appliedto broadside arrangen'ients of typical directive antenna ar 'angementsother than Wave antennae.

Referring to Fig. 1, a broadside connection, of three Wave-antennee A, Band C is shown although it Will be understood that the principle isapplicable to any number of antennae connected in broadside. Eachantenna is in the'form of a pair of Wires stretched across the countryside in line with the direction from which signals are to be received.yAssuniing that the wires extend from east to West, vfor cxan'iple, asignal coming from the east builds up by increments upon the Awires ofthe ivave antenna and reaches its maximum value at the West end of theantenna. lt is usually desirable to have the receiving apparatusconnected to the end of the antenna which points in the directionV fromwhich the signals arrive. Therefore each pair of Wires comprising anantenna, such as A, terminates at the west end in a Winding l of atransformer whose midpoint is connected to ground. rlhc groundconnection includes a primary Winding ll so related to the Winding 10that the two together constitute a transformer. rlhe transformerimpresses the received signal upon the two conductors constituting theantenna` A in such a manner that the conductors function as atransmission line to transmit the signal from the West or back end ofthe antenna, to the east or front7 end at which the receiving apparatusis located. At the front end the antenna, such as A, for example, isterminated in a similar transformer con'lprising primary Winding 12 andsecondary Winding- 13 for associating the antenna with a local line,such as A leading to the receiver. The midpoint of the Winding 12 isconnected to ground through a surge resistance 14.

A wave antenna such as above described has a directivediagram of thegeneral form indicated in'F ig. 2, so the niaxin'uim signal .is receivedin a direction along the axis ab from b-a. No signal is received from adirection along the axis cd. rlhe wave antenna is not, however, purelyunidirectional in its action but the directive curve has a smallback-end area 15 of somewhat irregular form, as shown in Fig. 2. Conpsequently a certain amount of noise or interference in a direction froma to o or from a direction at an angle somewhat less than 90 degrees oneither side thereof Will be superposed on the signal received by theantenna A, for example, as above described. In order to compensate orbalance out the noise which is picked up with the signal component dueto the back-end area 15 of the directive curve, a transformer having aprimary Winding 16 is provided, the secondary l? of the transformerbeing connected to a local line A2 leading to a. compensator consistingof a suitable phase adjuster '18 and attenuation adjuster 19. The noisefrom the directionsrepresented by the bachend area 15 will be mosteliiciently picked up by the coinluetors on the antenna A, functioningas a wave antenna for the direction from west to east. YThese noisecomponents attain their maximum value at the east or front end of theantenna and flow to ground through the surge resistance 111. By pickingup these components through the transforn'iers 1G and 17 and adjustingthem with respect to phase by the phase adjuster 18 and With respect toamplitude by the attenuation adjuster 19 these noise components may beimpressed upon the receiver in such phase relation and with such valueas to oppose the components picked up along vwith the signal due to thebach-end l5 of the directive curve. *When this compensation is properlyeffected for a sin lewave-antenna the directive diagram assumes the formshown in Fig. t, the bachend arca being reduced to zeroin a direction-from a to but being somewhat increased for directions in theneighborhood of degrees on either side thereof. It Will be understood ofcourse that by suitable phase adjustn'ient the compensation may be madeeffective for noise arriving from any direction within the so-calledbach-end area, the curve of Fig. s merely showing the condition, wherethe noise arrives in a direction of 1S() degrees from the desiredsignal.

So far the apparat-us has been described for al single Wave-antenna.lli/hen a plurality of antennae are arranged in broadside the other waveantennae, such as B and C, will be provided with equipment similar tothat described in connection with the ant-enna A. lThe signal from theantennae B and U Will be transmitted from the bach ends to the frontends thereof over the conductors of the antennae connected astransmission lincs, and the front ends of these antennae will beconnected to the receiver through lines such as B, and C1. Similarly thebalancing components will be taken from .the surge resistance ofantenn Band C through transformers similar to transformers 16 and 17 andcombined in the com]L ensating circuit through lines B2 and C2.

The signal components from the several antennae transmitted over theline circuits A'l, B1 and C, may be combined in a common circuit such asRL by a compound t ansformer such as RT, having individual lill) primarywindings in the circuits A1, B1 and C, and a common secondary in thecircuit RL. lt is ofcourse. necessary thatA the signal components i'ronithe several circuits should he impressed upon the circuit RL in phasewith each other. This resultI will be readily obtained where the linecircuits A1, l, and C, are of equal length. lV here the geographicalsituation is not such that these .lines would he normally oi equallength they may he made ot the same length by building the lines whichwould otherwise be short along indirect routes to; the antennaterminals. As an alternative the shorter lines may he made electricallyot the same length as the longest line hy includingl in the shorterlines artilicial line sections equivalent to the diil'erence in lengthbetween any given line and the longest line.

In a similar` manner the noise components talren from the surgeresistances o'i the sew eral antennae may he combined in acompensatin'gl circuit CL `through a compound transformer CT havingprimary windings associated with each ot' the lines A2, B, and C2 and acommon winding in the circuit CL. Here again components taken fromseveral antenna; must he impressed upon the common circuit CL in phasewith each other. The lines A2, B2 and C2 must there fore either be equalin length or be made electrically equal in length', as just described.The common circuit CL includes the phase adjuster 1S and attenuationadjuster 19, hoth ot which `are well known in the art. he former elementserves the purpose of adjusting the phase of the compensating currentdue to noise arriving from a given direction in the hack-end area so asto oppose the corresponding component received over lines A1, B1 and CVSimilarly, the attenuation adjuster i9 may he adjusted un. til thecompensating current is just equal in value to the noise currentcomponent in the circuit RL due to noise arrivingl from the particulardirection ,tor which compensation is to he made. As already stated thecompensation will he for noise arrivin from a. sector in thencighhorhood of i8() degrees from the direction ot' the signal.

As above described, the signal components are combined in a commoncircuit RL together with noise currents which are inherently picked upfrom the back-end area of the antenna system. rhe compensatingnoisecon'iponents are combined in a common circuit CL. vIn order that thesignal currents with their associated noise and the compensating noisecurrents 'trom the circuits RL and CL, respectively, may be combined inthe receiver, a compound transformer T may be employed. rihistransformer has separate primaries in the circuitsl'ii and CL and acommon secondary in the circuit `leading to the receiver. Thecompensating current is therefore combined with the currentto hecompensated in the same manner, so tar as electrical connections areconcerned, as the several components of the signal were combined, exceptthat the compensating currentpis 180 degrees out of phase fit-h thecurrent tohe compensated.

Neglecting for the moment the compensa- Y from a direction 135 degreesaway from the signal will be decreased. i j

As has been previously stated, the-practice heretofore hasiheen toattempt tofcompen-k sate each wave antenna separately. TWhile suchcompensation can he made it sutlicient tirnerand trouble be taken, as apractical matter it has been found very diiiicult. This will he clear ifwe consider the form of the directional diagram ot a single compensatedwave antenna, as shown in Figi. et. 'As has been previously pointed outsuch an antenna, when uncompensated, has a hack-end area such as shownat l5 in Fig. 2. lt the antenna he compensated *for noise arrivingiii-om a direction 180 degrees away from the direction of the signal,the back-end area is as shown in F el. N ow it will he obvious that ifthe only noise or interference is. trom a direction 180 degrees awayfrom the direction oit the signal, the operator who maires thecompensating adjustments can readily determine when the circuit isproper.- ly compel-mated at 15%() degrees. Since the noise from thatdirection is the only noise present, the tact of its disappearance willhe at once apparent.

n practice, however, the situation is not so simple. Static and otheriormsof noise and interference will usually he 'found coming fromvarious directions hroughout the entire haelt-end area. rThe operatorlistening on an uncompensated wave antenna hears all ot these noises. Itnow the ogiierator. begins to malte compensating adjustments thesituation will he that when the l" circuit is properly adjusted forcompensation the noise component arriving' from a d'ection 180 degreesaway from the signal will disappear hut noise components 'troni' adirection 45 degrees on either side thereof, for example, will haveheenk increased. In short, noise will he heard representing a largenumber oit components even though the single wave-antenna is properly`compensated.V rIhe result is that it is difficult,

r of Fig. 5.

and under certain conditions practically impossible, for the operator todetermine by the difference in the noise effects produced on thereceiver, when a single wave-antenna has been properly compensated.

The effect of the broadside connection (neglecting compensation) is,. asalready stated, to malte the diagram of less width. The back-end area,which assumed the form shown at 15 in Fig. 2 for a single wave antenna,becomes of the general shape shown at 15 of Fig. 3 for an uncompensatedtriple broadside antenna. IVhere all of the noise components arecombined in a single circuit, and phase and attenuation adjustments aremade for all of the antennae at the same time, as is the case with thepresent invention, the noise compenents arrivingl in a direction 180degrees from the signal will disappear when the proper compensatingadjustment has been made. The back-end area, which in the 'uncompensatedcondition has the form shown in 15 of Fig. 3, will be reduced to twosmall loops, as shown at 15 in Fig. 5. The operator will have nodidiculty whatever in determining when the circuit is properlycompensated because even assuming that noise is coming from a great manydirections within the back-end area the total noise will be verymaterially decreased when the components in the neighborhood of 180degrees away from the signal direction have been balanced.

In other words, an operator attempting to compensate a singlewave-antenna would have great difficulty, when noise is coming in from agreat many directions, in determining by hearing methods the differencebetween the back-end area 15 of Fig. 2 and the corresponding back-endarea` of Fig. 11 which represents the saine antenna compensated. On theother hand, the same operator would have no difliculty whatever indetermining the difference between the backend area 15 of Fig. 3 and theback-end area j This sharpness and definiteness of the balance obtainedin accordance with the present invention is due to the fact that thereis one and only one adjustment of the compensation that markedly re-`duces the area of the so-called back-end diagram. Hence this adjustmentis the only one which will materially reduce noise originating from arelatively broad sector behind the antennae.

In using the system of the present invention it is possible to reachthis adjustment with a minimum eifort at times when with the oldersystem it could only be reached by a-laborious process of cut and try ifindeed it could be reached at all. The present invention has theadditional advantage that the adjustments for proper combination of thesignal currents as well as for proper combina-tion of the noise currentswill be relatively stable and fixed in their nature, so that there onlyremains a single adjustment which need be made from time to time. Due tothe varied direction of noise and interference waves it is necessary atintervals to readjust the compensating' apparatus to preserve thedesired degree of bala-nce against these waves. In accordance with thepresent invention this is accomplished in a` minimum of time, whereas insystems previously used the broadside array must be separated into itscomponent antennae and each antenna adjusted for proper balance byitself. This complicated procedure necessarily entailed an interruptionof service involving a considerable length of time. Obviously of coursethe apparatus necessary to make the adjustments is in the present casematerially simpler and cheaper' than with the old system, particularlyif a. large number of antennae are to be used in broadside.

The description of the invention up to this point ha been concerned withthe arrangements for effecting a balance against the interferingcomponents impressed upon the receiver. rIhe method of obtaining thisresult, above described7 involves combining signal components fromseveral antennae arranged in broadside in a common circuit. Similarlyinterference components from the SQVGI'Il 311141211132@ 2LT@ COlDblHGd2].- COH11DOI1- circuit. These combinations are effected throughparallel connections extending between the common circuit and each ofthe antennae. @ne of the simplest parallel combination systems is thatin which the lines from the several antennae are connected to theprimaries of a number of 'dentical transformers whose secondariesconnected in parallel as shown in Figs. 6 and 8. An alternative is theuse of a multiple winding transformer as described in connection withFig. 1 and as illustrated in Fig. 7. The secondai'ies, or secondary, asthe case may be, may supply energy to the receiving equipment which mayor may not have a high input impedance, as is most convenient. Aparallel system of this type is adapted to supply energy to a filter orsimilar device which has a characteristic impedance of the saine orderas an open-wire line, thus conforming to standard telephone practice. Ofcourse other combining systems will readily suggest themselves and maybe used if necessary.

If the lines from several rantennae are directly connected to theseveral primaries, however, they cannot be terminated in theircharacteristic impedances. For instance, take the case of three antennaeas shown in Fig. 6. Here the line from each antenna would be terminatedin the impedances of the other two lines together with the inputimpedance of the receiving apparatus, all

being in parallel. This impedance would obviously be considerably lessthan the characteristic impedance of the line.

In accordance with the present invention it is proposed to overcomeythis difliculty by building out the transformers with impedance networksin such a manner as to t minatefall theplines in their `characteristicimpedances. In Fig. G `the combination is effected by three transformersRTA, RTB and RTC, in parallel. These transformers supply the receivingapparatus whose input impedance is K2. The impedance networks forbuilding out the transformers are shown as H networks Comprisingresistances r1, r2 .and r3. Since the characteristic impedance of mostlines at radio frequencies is very nearly equal to pure,resistance2onlyv resista-nce con'iponents need be used in the net-works in mostcases. y The characteristic iinpedances of the lines will be the sameand equal to K1. The 'values of the resistance elements `of an H networkwhich will satisfy' the theoretical requirements may he Vobtainedmathematically although the proc-- ess is somewhat complicated. Theadjustments of the resistance elements of such a network may also beobtained empirically Vwithin a fairly close approximation. or

example, if the two resistance elements r1' and the resistance element71 have a total value equal to the impedance K1, the `actual impedanceof the networks as seen fromthev line will not n'iaterially vary fromthat of 2r=-K2ip\,/K12+(n where n is the number of antennzefto beconibined and the 'other symbols are as previously defined.

lf K2 and K1 are the same this becomes If the common circuit in which.the lines are combined works directly into af vacuinn tube thein'ipedance looking .into the common circuit may be made very large. Vlnthis case K2 approaches infinity `and .theequation for r aen-1f (s) lAl/Jecomes wave antennae, yis equally applicable to broadthe line eventhough the combined impedances of the other two lines and the :receiverquite small, if the resistances 912 be made very large. In other words,if the resistances r2 are very large the shunting effect of theseresistances upon the resistance r3 will be relatively small. 1 i

The circuit in which the signal is combined andthe circuit in which' thecompensatingcurrent is combined may be brought together through similarindividual transformers T s and TC whose seeondariesare 4coma'ecte'd `inparallel, these transformers being built out .by networks similar to"those just described. Instead of using separate transformers forcombining signals a single compound transformer, having a plurality ofprimaries and a secondary, may' be used,

shown inFig. 7. Other ,combining arrangements, of course, may be used. Asimilar type of transformer may he used for ,combining the totalVsignaling current with the total compensating current. Here againifi-type networks are used for building out' the transformers in theindividual lines.

In actual practice 'H networks or other forms inyol vine shuntkelements. arenot necessari., as lsimple seriesresistanees fr may beused for building vout the transformer-sas shown in 8. 'l iis ligureissiinilar to 6 the use of individual transformers foreach line. Theresistances,la7V should `have the valuegivcn ybythe"eqinition,

side arrangements of other types of direc-y tive antenna systems. Forexample, '1T-ig. 9

shows .howthe invention inightbe applied 'to a lbroadside combinationofindividual directive antennae .units each comprising a` loop such asLA( worled in connection with a vertical antenna such as VA. Theceinbination of a loop and a vertical antenna, is well known, Ahas aone-'way directive edect somewhat similaritothat of a wave antenna. Ilffnew we provide a number of such combinations side by side and separatedfrom each 'other'by a fraction of a wave :length in a direction at rightangles `to the Idirection of maximum directiyity, each vertical antennaVof the broadside arrangements may be connected over aseparateline.through buildingout resistances" to a l'compoundcon'ibining *transformer suoli as .describes in connection with Fig. 1.Likewise, each of Athe 'loops` of 'the broadside arrangement maybeconnected over separate 4lines through building-out resista'nces to aVcompound transforn'iein he outputs of the vertical antennae are thuscoin- -bined in a `comi'non circuit RL, andthe outputs ofthe loops arethus combined in a connnoncireuit GL. lf a-.phafse adjusting device 18and an attenuation adjusting device 19 be included in the circuit CL thecircuit may be so adjusted as to balance out noise arriving from asector in the neighborhood ot 180 degrees away 'from the direction ot'the desired signal.

It is true that in this arrangement the phase and atenuation adjustmentsaifect both signal and interference components,

Vfor both signal and interference components are received by the loopsand by the verticals. However, due to the reversal of phase ot the loopcurrent with reversal. of signal direction it is possible, as is wellknown, to obtain a unidirectional characteristicas described. above.rllhe eii'ect of such a broadsirle array ot looi-and-vertical antennagroups is to secure a much sharper unidirectional characteristic thancan be obtained by using a single group oi this type.

llt is'also well known that two loops situated in tandem in the saineplane and a fraction ot a wavelength apart may be made to have a one-waydirectional effect. It a plurality ot such combinations are arranged inbroadside along an axis at right angles to the planes ot the loops themethod ot con'ibiiiing, heretofore described, may be applied, as shownin Fig. l1. Here the individual units comprise two loops, such as LA andLA, separated from each other by a distance which may be, for example,about one-twelfth ot the wave length in the direction ot the plane ot'the loops. Each combination of this kind may be separated 'from theadjacent combination in a direction at right angles to the plane ot thetwo loops by some fraction ot' wave length, such, for eX- ample, asone-half wave length. The loops7 such as LA, LB and LC, may be combinedin a common circuit RL by means of separate lines including resistancebuilding-out units through com pound. transformers of the type alreadydescribed. Similarly the'outputs of the loops LA', LB and LC may becombined in a common circuit CL through similar individual lines leadingto a. compoundtransformer through building-out rcsistances. The circuitGL includes a phase adjuster andv attenuation adjuster whereby the noisein the sector 180 degrees away from the signal direction may be balancedout without at the same time balancing` out the signal from the desireddirection. The principle in accordance with .which this result occurswill be similar to that already disclosed in connection with Fig. 9. Theresult accomplished is a more sharply unidirectional characteristic thancan be obtained from a single twoloop system, while retaining thefacility of balance against interferenceand noise as disclosed above inconnection with the application of the invention to wave antennae.

In addition to the advantages already re- :teired to the arrangements otthe present inventionhave certain other advantages. The use ot' vacuumtubes and other more oi less complicated apparatus which has been usedor suggested heretofore in connection with other systemsV combining theoutputs of anteiin is eliminated. in this connection it is assumed ot'course that the proper phase and amplitude relations are obtained bymeans oi suitable apparatus preceding the final combining apparatus.Aside 'from the question of siinplicity'it is ot course desirable toeliminate all vacuum tubes previous to the selective circuits ot thereceiver. The reason for this is that such tubes are liable to beoverloaded by interfering signals not in the lrequency range ot Ahereceiving apparatus.

rlhe system ot' the present invention may vbe' extended to any numberot' antennae and is adapt ble tor use with only one iilter preceding thereceiving apparatus.

T4. 'l l K 1l l l 1 is will be oovious that the principles .ieierfidisclosed may be embodied in many other i aiiiaations widely dii'lerenttroni those strated without departing from the spirit delined in the*l'ollowing illu of the invention as claims.

wWhat is claimed is: Y

l. ln a transmission system, a plurality of substantially one-waydirective antenna combinations arranged side by side a fraction ot awave length apart in a direotionat rightV angles to the direction fromwhich signals are to be received, a receiving circuit, a separateconnection from each antenna combination to said receiving circuit overwhich the desired signal may be transmitted together with noise lfrom asector in the neighborhood of 180 degrees from the direction of thesignal, means to combine the currents transmitted over said connectionsin substantially the same phase relation in said receiving circuit,arcontrolling circuit, separate vconnections from each antennacombination to said controlling circuit over which noise currentscorresponding to noises from a sector in the neighborhood of 180 degreesfrom the desired signal may be transmitted, means to combine said noisecurrents in said controlling circuit, means in said controlling circuitto adjust the phase and amplitude of the currents conibined thereinuntil the noise currents are substantially equal in amplitude butopposite in phase to the noise currents in said receiving circuit, andmeans to impress the currents of said controlling circuit upon saidreceiving circuit.

2. In a transmission system, a plurality of wave antennae arrangedparallel to each other and a fraction of a wave length apart in adirection at right angles to the direction from which signals are to bereceived, a

receiving circuit, a separate connection from each antenna to saidreceiving circuit over a sector in the neighborhood of 180 degrees fromthe desired signal, a controlling circuit, separate connections fromeachA of said conductors to said controlling circuit, means i'orcombining the currents `flowing over said last mentioned connections insaid control-` circuit so that the noise currents Will be oilsubstantially the same amplitude but opposite in phase to thecorresponding noise currents in the receiving circuit, and means toimpress the currents from said controlling circuit upon the receivingcircuit.

3. ln a transmission system, a plurality of -vavo antennae arrangedparallel to each other and a traction of a Wave length apart in adirection at right angles to the direction from which signals are to bereceived, each oi" said Wave antennae comprising a. pair of conductorsextending from itsiiront'end toits back end, means at the back end ofeach antenna to transmit to the conductors of the antenna acting as atransmission line the desired signal Wave built up at that end ot theantenna together With a. residuuni of noise from` a sector in theneighborhood of 180 degrees from the direction ot the desired signal, areceiving circuit, aseparate line associated with the front end oi eachantenna in such manner as to act as a continuation oi' the antenna as aline, each of said lines extending to said receiving circuit, means tocombine the currents from each of said lines upon the receiving circuitin substantially the same phase relation, a surge resistance associatedwith the front end of each antenna, a controlling circuit, separatedesired amount of noise currents flowing in such surge resistances uponsaid last inentioned connections, means to combine the noise currentsthus transmitted over the connections in said controlling circuit, meansto adjust the phase and amplitude of the combined current in saidcontrolling circuit so that the noise currents Will be substane tiallyequal in amplitude but opposite in phase to the corresponding noisecurrents in the receiving circuit, and means to impress the current fromsaid controlling circuit upon said receiving circuit.

si. In a transmission system, a plurality of directive antennacombinations arranged side by side and a fraction of a Wave length apartin a direction at right angles from the direction in which signals areto be received, a common receiving circuit, a `separate line extendingtrom each antenna combination to said Vreceiving circuit, a transformerarrangement or connecting said lines to said receiving circuit, meansassociated With each line for eiiectively building out the trans-:tormer so as to terminate each line in a combined impedance includingthat of the receiving circuit and other lines substantially equivalentto its own impedance.

5. 1n a transmission system, a plurality of directive antennacombinations arranged side by side and a fraction of a Wave length apartin a direction at right angles from the direction in which signals areto be received, a common receiving circuit, a separate line extendingfrom each antenna combination to said receiving circuit, a transformerarrangement for connecting said lines to said receiving circuit, andresistance combinations associated With each line having such values asto in elifect build out the trans- .former arrangements so that eachline Vis terminated in a combined impedance including that of thereceiving circuit and other lines substantially equal to its ownimpedance.

In testimony whereof, I have signed my name to this specification this2nd day oic June, 1926.

SAMUEL WV. DEAN.

Sti

